Problem Description

Given a sequence of positive integers and a positive integer $C$, compute the number of pairs $(A, B)$ such that $A - B = C$. Pairs with the same values at different positions are considered distinct.

Input Format

The input consists of two lines.

The first line contains two positive integers $N, C$.

The second line contains $N$ positive integers, which form the sequence to be processed.

Output Format

Output one line containing the number of pairs in the sequence that satisfy $A - B = C$.

4 1
1 1 2 3

3

Hint

Constraints:

• For $75\%$ of the testdata, $1 \leq N \leq 2000$.
• For $100\%$ of the testdata, $1 \leq N \leq 2 \times 10^5$, $0 \leq a_i < 2^{30}$, $1 \leq C < 2^{30}$.

Two new testdata sets were added on 2017/4/29.

Translated by ChatGPT 5